Hi,
I have tried what is suggested in Normalization uncertainties in VisualizeError - #4 by bibsession and it does not work in this case probably because the plots are projections from a RooSimultaneous pdf.
For a simple case adding the Normalization option works fine.
I will re-open https://sft.its.cern.ch/jira/browse/ROOT-9971 to track this problem
Lorenzo